Red blood cells may be more popular than white blood cells. It may be its most striking color, but at no time should we disregard the latter. Also called leukocytes, white blood cells are part of the blood cells that execute the immune response. Its main mission is to defend the organism from foreign substances or infectious agents.
However, their number does not always mean good news. The presence of leukocytes, for example, in the urine is associated with various conditions. If its level is elevated, it can also degenerate into disease. Therefore, today we will see why leukocytes in urine mean and what are the problems that could derive from them.
What are leukocytes?
As mentioned above, a leukocyte is a type of blood cell (hence it is often called a white blood cell) from the bone marrow. It is found in both blood and lymphatic tissue. As part of the immune system, their function is to help the body fight infections and various diseases.
There are many types of leukocytes. They are usually classified based on the presence or absence of granules (small inclusions that look like ‘stippling’ when the cells are viewed under the microscope: granulocytes or agranulocytes. The former are basophils, eosinophils and neutrophils, while the latter are monocytes and lymphocytes. Each one has some basic characteristics:
- Neutrophils. They are one of the first cells to react to infection. They are among the most numerous leukocytes and contain a wide variety of chemicals (enzymes, messenger molecules, etc.). When they are released at the site where an invasion is occurring, they attack the foreign structure and ‘call’ other defense cells.
- Lymphocytes. This is the second largest group of white blood cells in the body. There are 2 main types of lymphocytes: B lymphocytes (generate antibodies) and T lymphocytes (eliminate infected cells, cancer cells and control immune reactions).
- Monocytes. These are the ‘rearguard’ cells. If there is an external attack or in front of own dead cells to be removed from the organism, monocytes leave the blood and travel to the affected tissue. Once there, they will evolve into macrophages, cells capable of clearing an area by phagocytizing the attacker or the dead cell. Once inside, they will dump highly oxidizing molecules on top of the phagocytosed product. These will inactivate and destroy the foreign material. Macrophages are also capable of ‘alerting’ other cells that an attack is taking place. They will also be able to show the collected debris to other cells to generate specific antibodies against viruses or bacteria.
- Eosinophils. They are the main defense against parasites. They are also involved in allergy processes and, together with basophils, are the least abundant group of leukocytes in the blood.
- Basophils. They constitute less than 1% of leukocytes. They contain histamine, an indispensable molecule for the immune system. They are part of the defense against parasites, in allergic reactions, in atopic skin and asthma.
What do leukocytes in urine mean?
Urinalysis is one of the most demanded and common tests in a clinical analysis laboratory. For this purpose, a physical, a chemical and a microscopic analysis of the urine is always performed. In addition to studying the results of cells and bacteria, the presence of leukocytes in urine is also analyzed.
An elevated number of red blood cells in the urine sediment (red blood cells) is called hematuria. The presence of an elevated number of leukocytes (white blood cells) is called ‘leukocyturia’.
The presence of a certain, low number of leukocytes (up to 5 per high-resolution field, at a field of 400x magnification) in urine may be normal. Even a slight increase in their number should not alarm us. In most cases it is a minor health problem. Urine white blood cell test results should always be correlated with the patient’s health status (symptoms, history of any disease, medication intake, etc.).
Why can leukocytes appear in the urine?
The first thing that is usually thought if leukocytes are found in the urine is that it is caused by a urine infection. However, there are other causes:
Urine infection. As mentioned above, it is the first thing you think of if there are a lot of leukocytes in the urine. In fact, this is the most common cause, especially in women. It may result from cystitis or pyelonephritis. Cystitis is caused by bacteria and its symptoms may be burning and/or pain when urinating, frequent urination, cloudy color and foul-smelling urine, and sometimes weakness, tiredness and fever.
These symptoms appear suddenly, without warning and with varying intensity. Kidney infection or pyelonephritis is one of the most serious infections and is accompanied by pain, frequent urination, high fever, chills, tachycardia and vomiting. If the patient is immunosuppressed or has been using a urinary catheter for some time, he or she is much more likely to develop a kidney infection. A urinalysis will detect, in addition to the number of leukocytes, bacteria and nitrites.
Urine infection without bacteria. It is also possible to have leukocytes in urine and suffer symptoms of bacterial infection without such infection being demonstrated. This means that even if a patient has symptoms, no bacteria will be found in the sediment or culture. This phenomenon is called sterile leukocyturia. If a urinary tract infection has been ‘decapitated’ by an antibiotic treatment, not finished or with partial resistance of the germ to the antibiotic used, this case occurs.
Sterile leukocyturia may be caused by sexually transmitted diseases, virus or fungal infections or even tuberculosis. In these cases, it is necessary to carry out a special cultivation or additional tests to demonstrate the presence of these germs.
Bacteria in the urine without symptoms. In this case, bacteria are found in the urinalysis but the patient does not develop symptoms. Asymptomatic bacteriuria is not usually treated with antibiotics. This treatment is only performed when the person is at high risk for urinary tract infection if left untreated.
Acute and chronic prostatitis. This disease only occurs in men. Symptoms are painful and difficult urination, frequent urination (especially at night), fever and chills. The patient may also experience pain in the abdomen, pelvis or lumbar region. This disease is very rare and appears with repeated episodes, as if it were an acute infection (increased frequency, urgency and stinging when urinating). No symptoms should appear between episodes.
Lithiasis or urinary tract stones in the kidney or urinary tract. In a urinalysis with Lithiasis we will find leukocytes, erythrocytes and crystals. However, there should be no bacteria. Symptoms of this disease are lower back pain, difficulty urinating, decreased urine output, nausea, vomiting, chills and fever.
Glomerulonephritis (Non-infectious nephritis). This acute inflammation of the kidney (either as a debut of the disease or as a flare-up of an already known disease) has a wide variety of symptoms (decreased urine output, shortness of breath, headache, fatigue, pale skin, swelling). The number of leukocytes in the urine is much lower in this case than in the case of an infection. The ones we find may be eosinophils. If a blood test is done, kidney function will be affected.
Systemic lupus erythematosus. In urine with systemic lupus erythematosus, a large number of leukocytes will be seen, in addition to proteins and erythrocytes. This autoimmune disease can cause inflammation in the joints, skin, eyes and kidneys.
Interstitial cystitis. It is a disorder of usually unknown causes and of long duration. Symptoms include discomfort or pain, pressure and increased sensitivity in the bladder area, lower abdomen and pelvic area. This list of effects may vary from person to person, as well as their intensity.
Urine retention. It occurs when urine accumulates in the bladder and the presence of bacteria increases the risk of infection. This situation may increase leukocytes in the urine.
Use of some medications.Certain medications (antibiotics, aspirin, corticosteroids, diuretics) may cause the appearance of leukocytes in the urine (in this case, eosinophils).
Cancer. Some tumors such as bladder, prostate or kidney tumors can generate leukocytes in the urine. These situations cause the immune system to weaken. It may also be the case that leukocytes appear as a consequence of the treatment performed against these tumors.
Conclusions
The treatment of an elevated number of leukocytes in the urine depends entirely on the cause. Only a correct diagnosis will allow us to get the treatment right. In most cases it is not necessary to perform active prophylaxis.
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